Revealing mistake: When Ed and Dexter are in the ventilation shaft, watch when they fall in the trolley thing. If you look carefully you can see Ed's wig hanging on the edge. It's got a good burger hat on it.
Revealing mistake: When the guy asks for a good shake and the weird kid shakes him you can see the people that work at the fast food restaurant moving back and forth very rapidly. This makes the shaking scene an obvious rewind and playback sequence.